Liquid bioinoculant formulation has become the preferred technology to solve the problems associated with shorter shelf life, high contamination, poor quality, low field performance and processing solid carrier in carrier based bioinoculant formulation. In the present study, attempts were made to enhance the survival/ shelf life of liquid rhizobial inoculants (Rhizobium sp. strain MB703) through addition of additives such as glycerol, polyvinyl pyrollidone (PVP) and gum arabic (GA) for their ability to support growth and promote survival in yeast extract mannitol broth (YEMB) during the storage. All liquid rhizobial inoculants prepared in amended media showed higher viable count in comparison to inoculants prepared in YEMB (control) at 180 days (d) of storage. Maximum log no. of cells were obtained in inoculants prepared in YEMB amended with 2% GA followed by YEMB + 1% GA and YEMB + 2% PVP. Mungbean (Vigna radiata L.) seeds treated with 90 d old liquid rhizobial inoculants of strain MB703 amended with 1% PVP or 2% glycerol enhanced plant growth as compared to uninoculated control.
